Wall structure 36.5 Poroton T8 including clinker

What is still missing is the motivation for the change of mindset.

24cm masonry 12cm mineral facade insulation with fleece 1cm air layer 11.5cm facing brick

It's almost 50cm again. Why? Passive house standard desired? Otherwise, I don't understand the 24cm masonry. Air layer is unnecessary.

Is it really necessary to build here compulsively with Poroton (24cm plus insulation)? Has the "indoor climate" marketing taken effect?

Personally, I don't see 50cm as a drama. With a two-shell construction, you are always over 40cm. In my opinion, you don't have to worry about a few centimeters more or less.

Personally, I don't see 50cm as a drama. With a double-shell construction, you are always over 40cm. In my opinion, a few centimeters more or less shouldn't cause you to overthink it.

Well, with KS it would only be 41cm. That means a lot of space is lost. Not to mention the different lighting feeling or the optics with thinner exterior walls.
The 50cm calculated by the OP have exclusively disadvantages.

There is a boundary that runs across the country; north of it, [Ytong o.Ä.] or KS are used, south of it they use Poroton or relatives. However, both have warm dry houses.

So Ytong can now be seen here in the south in at least one new housing development. It is no longer quite so clearly separated.